feat(cli): support Fn::ImportValue intrinsic function for hotswap deployments

[tomwwright]

Purpose 🎯

Extend the EvaluateCloudFormationTemplate class to support the Fn::ImportValue intrinsic function. This allows for more diverse templates to be evaluated for the purposes of determining eligibility for --hotswap deployments

Closes #21320

Approach 🧠

Implement LazyLookupExport in similar fashion to LazyListStackResources to cache required CloudFormation API calls (preference was to implement using a generator function instead so style is not entirely consistent, is this an issue?)

Add some basic unit tests for EvaluateCloudFormationTemplate.evaluateCfnExpression() is they were absent, then add some tests for Fn::ImportValue

Todo 📝

• Update doco where appropriate
• Add to hotswap deployment tests
• Look for appropriate integration tests to update

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

The pull request linter has failed. See the aws-cdk-automation comment below for failure reasons. If you believe this pull request should receive an exemption, please comment and provide a justification.

A comment requesting an exemption should contain the text Exemption Request. Additionally, if clarification is needed add Clarification Request to a comment.

[tomwwright]

Exception Request: Features must contain a change to an integration test file and the resulting snapshot.

I've reviewed the integration tests for packages/aws-cdk and I don't see a relevant test to update -- can someone indicate which would be appropriate, or confirm that this feat doesn't touch any?

[tomwwright]

Clarification Request: CLI code has changed. A maintainer must run the code through the testing pipeline

I'm not certain on how to action this one -- could someone help me get this linter request resolved?

[tomwwright]

Have rebased to tip of main to resolve conflicts

[tomwwright]

@vinayak-kukreja added the doco link and rebased to tip of main to update -- let me know if there was anything else pending!

[aws-cdk-automation]

This PR has been in the CHANGES REQUESTED state for 3 weeks, and looks abandoned. To keep this PR from being closed, please continue work on it. If not, it will automatically be closed in a week.

[vinayak-kukreja]

Hey @tomwwright , the PR looks good to me. Running it through our test pipeline again with the merge from main. Will approve the PR if the workflow passes.

[vinayak-kukreja]

Hey apologies for the delay. We are facing some issues with our test pipeline. I will update here as I get a chance to run this PR through the pipeline.

[aws-cdk-automation]

➡️ PR build request submitted to test-main-pipeline ⬅️

A maintainer must now check the pipeline and add the pr-linter/cli-integ-tested label once the pipeline succeeds.

✅ Updated pull request passes all PRLinter validations. Dismissing previous PRLinter review.

[vinayak-kukreja]

Hey @tomwwright , the pipeline run was successful. Thank you for contributing to the cdk. Really appreciate your effort.

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 79cb2c7
• Result: SUCCEEDED
• Build Logs (available for 30 days)

Powered by github-codebuild-logs, available on the AWS Serverless Application Repository

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[tomwwright]

Thank you for your review @vinayak-kukreja 🙌